Dish radiator of adjustable polarization



Aug 15, 1961 E. F. HARRIS DISH RADIATOR oF ADJUSTABLE PDLARIZATIDN Filed Dec. 26, 1957 Hummm Z2 iwf INVENTOR.

by a source of radiant energy at its focus. .the communications channel is a line-of-sight path be- -the same.

2,996,714 DISH RADIATOR F ADJUSTABLE POLARIZATION Edward F. Harris, Lincolnwood, lll. (6412 W. Lincoln Ave., Morton Grove, Ill.) Filed Dec. 26, 1957, Ser. No. 705,338 3 Claims. (Cl. 343-756) Microwave radiations, such as those of 6,000 megacycles, are radiated with a high degree of directivity and with good eiciency by a parabolic or dish reflector fed Typically,

tween two towers, each either provided with a dish antenna at its top, or with a 45 degree reector which is in turn in energizing relationship with a horizontal dish antenna pointed upward from the bottom of the tower.

The antenna beam width should be at a minimum value in the interest of providing maximum effective radiated energy and of minimizing interference. Typically, it may be of the order of 3.5 degrees in both the E plane and the H plane. However, -this high directivity makes the cornmunications system particularly sensitive to slight movement of the dish reflector or the energizing mechanism therefor due to ice, water and wind loading. It is accordingly important to provide a dish radiator that is of rigid construction.

It is further necessary to align the transmitting and receiving mechanisms so that the polarization of each is This due to the practical fact that the dish radiator is most conveniently fed from a rectangular wave guide which is energized by waves having a denite axis of polarization, and the waves as reflected partake of the same polarity. Heretofore, the necessary polarity adjustment has been made at the reflector feed point, a position where adjustment is dilicult, especially in the case of dish antennas mounted on towers.

In accordance with the present invention a rigid dish antenna is provided by supporting the dish on a frame defined by rigid spider members, preferably pipes, laid on a common plane, from which a plurality of posts extend and are aflixed to the dish itself at points spaced from the center. At least one of the spider members extends radially from the dish and is aiixed, outboard of the dish, to a circular energizing wave guide which forms a continuation thereof. The energizing wave guide in turn sweeps forwardly of the spider member to which it is axed, over the edge of the dish, and inwardly to terminate in a radiating window at the focus of the paraboloid delined by the dish. Further support for thc energizing wave guide is provided by an auxiliary support post extending from the spider member through a window in the dish, tothe energizing wave guide. The latter post and the portion of the spider member adjacent the energizing wave guide are provided with couplings for easy disassembly.

The energizing wave guide terminates in a rotatable wave guide transition coupler. This coupler at its opposite end has a rectangular window to receive the end of a exible rectangular wave guide. The polarization of the radiated energy (or the polarization of the energy most effectively received) is determined by the position of rotation of the wave guide transition coupler, a cornparatively easy adjustment since it is located outboard the antenna proper.

LIt is therefore a general object of the present invention to provide an improved dish type antenna.

Further it is an object of the present invention to provide an improved dish type antenna characterized by rigidity of construction.

Stiil `another object of the present invention is to provide an improved dish type antenna structure in which a 2,996,714 Patented Aug. 15, 1961 rigid frame supports the reflector dish and no parts are supported by the rellector dish.

Yet another object of the present invention is to provide an antenna of the foregoing type that is readily disassembled for comparatively flat shipment.

Another and further object of the present invention is to provide an improved dish type antenna in which the polarization of the radiated energy is readily adjusted without disturbing the antenna itself.

Further it is an object of the present invention to provide an improved dish type antenna having a rigid reecting and energizing structure of symmetrical conformation adapted to handle waves of any polarization, together with rotatable transition coupling elements located outboard said structure and adapted to feed the same with wave energy of adjustable polarization.

lt is still another object of the present invention to provide a dish antenna ofthe foregoing type characterized by features of construction, combination, and arrangement making it simple and inexpensive in construction, light in weight, small, eicient, and adapted for installation in a wide variety of practical installations.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objectives and advantages thereof, will best be understood by reference to the following description taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is atop plan view of an antenna constructed in accordance with the present invention;

FIGURE 2 is a view in cross-section with parts in elevation of the apparatus of FIGURE 1;

FIGURE 3 is an enlarged cross-sectional view of the axis 3--3, FIGURE 1; and

FIGURES 4 and 5 are somewhat enlarged fragmentary cross-sectional views through axes 4-4 and 5 5, FIG- URE 3.

Referring now to FIGURES l and 2, the antenna of the present invention consists of a spun aluminum dish 10, which is in the shape of a paraboloid of revolution. As shown in FIGURE 2, the dish 10 has a downwardly turning lip 10a about its periphery and is supported by four vertical posts 12 and 12a which are in turn welded to and supported by the four spider arms 1-4 and 14a, respectively. It will be noted that the dish 10 has a vertical axis of symmetry and that the spider arms 14 and 14a, are radially disposed in relation to this axis and are located in a plane transverse to this axis. The dish 10 is aliixed at its periphery to the posts 12 and 12a by any suitable means which may, for example, be by welding the ends of these posts being beveled as shown in FIG- URE 2 to receive the dish. While the respective arms and the respective posts are shown as unitary members, these may, if desired, be separate members aliixed to each other by welding or similar means.

A radial arm 16 is provided in the nature of an extension on the spider arm 14a and post 12a and in somewhat raised or offset relation to the arm 14a as is shown in FIGURE 2. This extension terminates in the ange coupling 16a. A like pipe member 18, having a ange coupling 18a is atiixed to the pipe 16 and flange 16a. This is accomplished by suitable bolts (not shown) which extend through openings provided in the respective flange coupling.

At its outboard end the arm 18 is beveled at 1gb and is welded to the sloping circular wave guide indicated generally at 22. It will be noted that this wave guide terminates in a ange coupling 22a which is parallel to the members 16 and 18 and spider arm 14a but is 1ocated between their respective axes. The circular wave guide 22 extends upward and over the edge 10a of the dish 10 as is shown in FIGURE 2 and at 22b bends toward the concave side of the dish reflector 10 to terminate at 22C at the focus of the paraboloid defined by the dish 10. At this point the wave guide 22 has a window of Mylar or similar thin dielectric material (not shown) having low loss characteristics in the centimeter wave region.

The wave guide 22 is supported in relation to the spider defined by arms 14 and 14a, by the upstanding post 24 which is welded to the arm 14a, extends upwardly through a suitable opening in the dish l0, and terminates in the flange coupling 24a. A similar depending post 26 is welded to the wave guide 22 and extends downwardly as shown in FIGURE 2 to terminate in the flange coupling 26a. The flange portions of couplings 24a and 26a have mating openings which receive bolts (not shown) which are secured together to provide a rm mechanical support.

The wave guide 22 receives a wave guide transition coupler indicated generally at 2S, at the tiange end portion 22a. As shown in FIGURE 3, the coupler 28 terminates in an outwardly extending flange 28a which seats against the annular face of the flange coupling 22a as shown in FIGURE 3 to define a continuous cylindrical inside face. A slip coupling 23 overlies the iiange coupling 22a and is releasably secured to the flange 28a by the bolts 25 and nuts 25a. As shown, the flange 22a has an outer annular recess which receives the resilient -ring 27 of rubber or like material. It will be noted that an annular compression face 29 is formed between ange 22a and the slip coupling 23, thus rigidly securing these parts together when bolts 25 are drawn tight.

At the end opposite flange 28a the coupler 28 has a second flange 28e. This flange mates with the flange 36a of the iiexible rectangular wave guide 36 as is shown in FIGURES l and 2. These two flanges are held together by suitable bolts (not shown).

The wave guide transition coupler 28 provides a smooth transition between the rectangular opening in the iiexible wave guide 36 and the circular opening in the wave guide 22. To this end, the cross-section of the opening in the coupler 28 is rectangular adjacent the wave guide 36, as seen in FIGURE 4. However, when viewed from the opposite end, as in FIGURE 5, the crosssection of the opening in coupler 28 is circular and smoothly and gradually convergent to the rectangular conformation `as shown.

The iiexible wave guide 36 may be any one of the flexible wave guide constructions well known to the art. One such construction consists of a rectangular length of heavy rubber having a rectangular bore of the desired size, the inner face of which is covered by a highly conducting coating of material which is adherent to the rubber. Thus a low loss wave guide is formed having the same ability to twist and bend as does the rubber itself. At the free end (not shown) the flexible wave guide 36 is affixed to a source of radiant energy for transmitting purposes or, for receiving, to :a suitable receiver.

It will be observed from the foregoing that the wave guide 22 issupported in relation to the dish l0 by the spider and not by the material of the dish. This is an important feature since the dish, of thin material, can readily flex in diaphragm action, and thus necessarily is incapable of giving a rigid and firm support to wave guide 22. Since effective operation of the complete unit demands that the termination 22e of wave guide 22 be located on the focus of the paraboloid, it is important to provide this fixed support.

It will be `further noted, that the post formed by members 24 and 26 does not interfere or alter the pattern of radiation. This is because the tube 22 itself shadows the dish 10, and the post thus formed in no Way alters the face or position of the shadow.

The polarization of the radiations in the wave guide 22 is determined by the orientation of the wave. guide coupler 28 land the rectangular opening in wave guide 36. In the case of a transmitter, the cavity 40 of wave guide 36 is energized by waves having definite polarization, the H plane of the waves being along the lengthy side of the rectangular cavity and the E plane being along the narrow side of the rectangle. In any event, as these waves travel into the circular wave guide 22 the polarization remains unaltered since the coupling 28 includes nothing to shift the plane of polarization. The waves then travel through the Wave guide 22, without alteration of their polarization and are accordingly radiated into the reflector 10. The latter reflects the waves without greatly altering their polarization, so that the polarization of the radiated beam is determined by the position of rotation of the coupler 28 in relation to the circular wave guide 22.

When the coupler 28 is rotated in relation to the wave guide 22, the orientation of the rectangular opening 40, FIGURES 3 and 4, of the coupler (and hence the flexible wave guide 36) is changed. This varies the polarization of the Waves as they travel to the wave guide 22, and hence the polarization of the radiated energy.

For receiving purposes, the above adjustment determines the plane of polarization for which maximum sensitivity is obtained.

The above construction should be contrasted with those heretofore used. The polarization is achieved by the simple rotation of the coupler 28, achieved by releasing bolts 2S. It is unnecessary to readjust or alter any parts of the antenna proper. The coupler 28 can be located at a position where it can be conveniently adjusted.

In an actual antenna constructed in accordance with the present invention the wave guide 22, as well as the tubes 1S, 14, 14a, 12, 12a, 2li and 26 was constructed of 1.6 inside diameter aluminum tubing with an outside diameter of 1.9". The coupler 28 was an aluminum casting 8 long. The opening at the rectangular end of this wave guide was 1.372 by 0.622". The end 22e of the parallel wave guide was covered with a Mylar sheet 0.01 thick and was located l2 from the central point of the reector 12, this being the focus of the paraboloid. The dish 10 was of spun aluminum having a diameter of 40".

With the above antenna effective operation was secured at frequencies from about 5900 megacycles to about 8000 megacycles. Over this frequency range the standing Wave ratio was no greater than 1.2, the beam with in both planes was of the order of 3.5", the front to back ratio was about 40 db, the side lobes were about 23 db @down and the aperture etiiciency was of the order of 60 a.

While I have shown and described a specific antenna construction embodying the present invention it will, of course, be understood that various modifications and a1- ternative constructions can be made Without departing from the true spirit and scope of the invention. I therefore intend by the appended claims to cover all such alternatives falling within the true spirit and scope thereof.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A dish antenna of adjustable wave polarization, comprising: a reflecting dish of extent suii'cient to act as a reiiector; a circular wave guide of diameter suicient for wave guide action, said guide terminating at one end in an aperture through which radiant energy is directed between said wave guide and reflector and at the other end extending outboard the dish; means connecting the wave guide and dish in immovable relationship; a Wave guide transition coupler having a longitudinal slot terminating at one end in a circular conformation of like size as said wave guide and at the other end in a rectangular conformation to receive a rectangular wave guide, the slot having gradually changing cross-Section to provide a substantially non-retiecting transition from rectangular to circular conformation a wave guide feed mechanism attached to the other end of the transition coupler for rotation therewith and effective to feed radiant energy into said other end thereof polarized along an axis of the rectangle dened by said slot, and means connecting said one end of the coupler to the said other end of the circular wave guide, said means permitting rotation of the coupler in relation to the circular Wave guide to vary the orientation of the wave guide feed mechanism in relation to the circular Wave guide.

2. A dish antenna of adjustable wave polarization, comprising: a circular reection dish of extent sufficient to act as a reflector; a circular Wave guide of diameter sufficient for wave guide action, said guide terminating at one end in a window facing the concave surface of the dish through which wave energy is directed between said guide and reflector; means connecting the Wave guide and dish in immovable relationship; a wave guide transition coupler having a longitudinal slot terminating at one end in a circular conformation of like size as said wave guide to couple Wave energy thereto and at the other end terminating in aA rectangular conformation to receive Wave energy of predetermined polarity, said slot having a gradually changing cross-section to provide a substantially non-reflecting change from rectangular to circular conformation; means connecting with one end of the coupler to the said other end of the circular wave guide, said means permitting rotation of the coupler in relation to the circular Wave guide.

3. A radiating mechanism `of adjustable wave polarization comprising in combination: a radiating mechanism adapted to radiate along a predetermined axis and of symmetrical conformation about that axis; a circular wave guide ixedly supported in relation to the radiating mechanism and terminating at one end on said axis to transfer radiant energy in relation to said radiating mechanism; and a wave guide transition coupler having a longitudinal slot terminating at one end in a circular conformation of like size and in registry with the other end 0f the wave guide and at the other end in a rectangular conformation to receive an energizing Wave guide capable of rotation, said slot having gradually changing cross-section to provide a substantially non-reflecting transition from rectangular to circular conformation; said coupler being rotatable in relation to the circular wave guide to vary the orientation of the rectangular wave guide in re1a tion thereto.

References Cited in the tile of this patent UNITED STATES PATENTS 2,531,455 Barrow et al. Nov. 28, 1950 2,540,518 Gluyas Feb. 6, 1951 2,703,842 Lewis Mal'. 8, 1955 2,768,354 Hogan Oct. 23, 1956 2,786,998 Davis Mar. 26, 1957 

